The usable lifetime of ferroelectric devices whch include phase III potassium nitrate is determined by three parameters: (1) the phase III crystalline structure stability of the potassium nitrate; (2) the number of read/write cycles that can be accomplished before the output voltage is less than a predetermined usable level; and (3) the length of time a memory bit will retain information.
Phase III potassium nitrate in bulk material is an unstable phase at normal room temperature and pressure. The present invention involves the use of a stable thin film of potassium nitrate, and it is the processing parameters which determine the stability of the phase III configuration. The only accurate test to determine the long term stability of phase III potassium nitrate is in real time.
The art is exemplified by U.S. Pat. Nos. 3,483,447; 3,405,440; 3,213,027; 3,305,394; 2,916,681; 3,132,326; 3,460,103; 3,414,435; 3,728,694; 3,142,044; 3,728,694 and 3,939,292; Canadian Pat. No. 747,459; RCA Technical Notes TN No. 8223-17-69 "Reduction of Waiting Time Effects in Ferroelectrics" by George W. Taylor, pages 1-3; IEEE Proceedings of the Twentieth Electronic Components Conference, May 13-15, 1970 "Progress Toward a Fast, Non-Volatile, Non-Destructive Read Out Memory Element Utilizing KNO.sub.3 " by Richard C. Born et al, pages 149-154; 1970 Michigan Technological University Thesis "Progress on a Thin Film Potassium Nitrate Ferroelectric Memory" by George Andrew Rohrer; 1969 Proceedings of the Electrochemical Society entitled "Thin Film Dielectrics", edited by Frederick Vratny, pages 237-53; paper entitled "Dielectric Behavior of Films of Vacuum-Deposited KNO.sub.3 " by J. P. Nolta et al; 1971 Michigan Technological University Thesis entltled "Investigation of a Thin Film Ferroelectric Memory Device Utilizing KNO.sub.3 " by John W. Loney; and "A Proposed Fast-Access Large-Capacity Ferroelectric Memory", by D. W. Chapman, Systems Development Division, IBM Corporation, San Jose, California.
The present invention avoids the drawbacks and disadvantages of the prior art and is superior thereto on the basis of the above-mentioned three parameters.